Sensor device and method for arranging a sensor device on a mounting plate

ABSTRACT

The invention relates to a sensor device containing a housing ( 1 ) and a spring element ( 9 ) comprising a guiding element ( 5 ) for displacing the sensor device over a mounting plate ( 7 ) in a guided manner. Said guiding element ( 5 ) co-operates with a guiding means ( 12 ) of the mounting plate ( 7 ). In a mounting position of the sensor device, said sensor device engages in the mounting plate ( 7 ) and is fixed to the same.

CLAIM FOR PRIORITY

This application claims priority to International Application No.PCT/DE01/03430 which was published in the German language on Sep. 6,2001.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a sensor device and a method forarranging a sensor device on a mounting plate of a motor vehicle.

BACKGROUND OF THE INVENTION

Airbag and belt-tightener units are important passenger-restrainingmeans for protecting motor vehicle passengers in the event of anaccident involving a frontal or side impact. Signals from sensor devicesare used for deciding when to release the airbag or belt-tightener unit.Acceleration sensor devices, in particular, are fitted centrally in theairbag controller or non-centrally at another point in the vehicle.Central is deemed here to refer in particular to the position in thehousing of an airbag controller which is usually fitted under thecentral console in the motor vehicle. Consequently, any fitting of acontrol or sensor device outside the airbag controller is referred to asnon-central or external. Non-central sensor devices are therefore oftenreferred to as airbag satellites or simply as satellites.

It is important in the case of acceleration sensor devices, inparticular, to achieve a mechanically highly rigid coupling of theairbag satellite with the vehicle body. If this does not exist, themechanical transfer function between satellite and vehicle body changes,and the satellite transmits in part falsified signals. For mountingexternal airbag controllers, in the main metallic mounting plates, onwhich the satellites are rigidly fastened by means of screws and counterscrews, are fitted in the motor vehicle.

The sensor signals are evaluated in the airbag satellites themselves orin the central airbag controller by algorithms which have to be adaptedfor each vehicle type. The computational results of the algorithms arefrom time to time very different for different mounting locations.Especially in the case of acceleration sensor devices, it is thereforeparticularly important to mount the airbag satellites reproducibly atthe same point on the vehicle body, since only in this way can the sameevaluation of an impact event be guaranteed for all the vehicles in avehicle line. Special mounting aids and mounting procedures whichprevent any incorrect positioning of an airbag satellite are thereforeused in production in the automotive industry.

FIGS. 5 a and 5 b show a known mounting aid in the form of a mountingcover 3 which is placed on a housing 1 of an airbag satellite. FIG. 5 ashows the airbag satellite before installation in the motor vehicle. Inthis arrangement, the fastening screws 4 cannot be tightened, as themounting cover prevents access with a mounting tool. Only in theinstallation position intended for that purpose, as shown in FIG. 5 b,can the satellite be fastened to a mounting support.

FIGS. 6 a and 6 b show the same two arrangements of the satellite on amounting plate 7, viewed from the back.

The two FIGS. 6 a and 6 b illustrate the known method for mounting anairbag satellite:

-   -   The housing 1 is placed on a mounting plate 7 using a        positioning aid 8 (FIG. 6 a).    -   The housing 1 of the satellite is then displaced in the        direction of the arrow (FIG. 6 b).    -   The satellite is then fastened to the mounting plate 7 through        the cooperation of mounting means.

A disadvantage of this known mounting aid is the two-part formation ofhousing and the mounting aid, in particular a mounting cover. The use oftwo separate components in the production of an airbag satellite entailsa high additional logistical outlay. This comprises the handling of agreater number of components and an additional process step in which ahousing and a mounting cover have to be assembled.

SUMMARY OF THE INVENTION

The invention is to enable reproducible positioning of an airbagsatellite in a motor vehicle with high positioning accuracy appropriateto its use.

The sensor device according to one embodiment of the invention includes,in addition to its housing, a spring element with a guiding elementarranged thereon, the two of which together replace the known mountingcover.

A guiding element refers here to any type of construction which canengage in a guiding device, in particular a lug into a through recess ofa mounting plate.

On the other hand, the guiding element can conversely be fashioned suchthat, when being mounted, a guiding device of the mounting plate engagesin the recess of the sensor device, in particular a lug of the mountingplate into a cavity in the housing.

A sensor device with a guiding element on a mounting plate according toone of the two proposed designs can preferably be displaced in thedirection which is predetermined by the guiding device.

An advantageous further embodiment of the invention is the springelement with its guiding element as a part of the housing, in particularof a housing made of plastic or metal. The described disadvantage of themounting cover can be avoided by the invention. Compared withmanufacture of a sensor device having a mounting aid comprising twoparts, production is simplified substantially.

The formation according to the invention of the sensor device enables asimple method for arranging a sensor device on a mounting plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in detail below withreference to schematic diagrams, in which

FIGS. 1 a and 1 b show a perspective view from two sides of a sensordevice according to the invention.

FIGS. 2 a and 2 b show the sensor device according to FIGS. 1 a and 1 bon a mounting plate in an initial position and in a final position.

FIGS. 3 a and 3 b show the sensor device according to FIGS. 2 a and 2 bfrom a different viewpoint.

FIG. 4 shows a sensor device for displacing the satellite to themounting position.

FIGS. 5 a and 5 b show a perspective view of a known sensor device witha mounting cover in an initial position and in a final position.

FIGS. 6 a and 6 b show the known sensor device according to FIGS. 5 aand 5 b from a different viewpoint.

FIG. 7 shows a sensor device for an alternative method for engaging thesatellite in the mounting position.

The same elements and components of the embodiments are labeled in theFigures below by means of the same reference symbols.

DETAILED DESCRIPTION OF THE INVENTION

The sensor device is referred to below also as an airbag satellite orsatellite.

FIG. 1 a shows a sensor device comprising a housing 1 and comprising aspring element 9 with a guiding element 5. The spring element 9 has twosubstantially parallel spring bars 11, the ends of which are fashionedin one direction as guiding lugs. These are suitable for engaging as aguiding element 5 in recesses of a mounting plate 7 fashioned as aguiding means 12. An arrangement is deemed substantially parallel herein which the two spring bars 11 form preferably no angle to one another,but at most an angle of 15 degrees.

In order to protect the spring bars 11 against mechanical overload whendeflected, a further part of the spring bars 11 serves as a springtension limiter 13.

The two ends of the spring bars 11 are connected to one another via anelastic connecting bridge 10.

As an advantageous further embodiment of the invention, the spring bars11 with the guiding lugs 5 and the connecting bridge 10 are in theembodiment fashioned in one piece with the housing 1 of the sensordevice. The sensor device includes therefore of fewer components, as aresult of which the outlay in respect of production and assembly isreduced.

Fastening screws 4 are also to be seen as mounting means. These aresuitable for cooperating with the corresponding counter screws asmounting counter device so that the satellite can be fastened on amounting support in the motor vehicle. Alternative mounting devices arecombinations of fastening screws and screw threads or other mechanicallyrigid forms of connection such as snap-on connections, riveted joints,etc. Fastening screws and screw threads find the necessary counter-holdon the opposite side of a mounting plate in the form of mounting counterdevice, in particular counter screws, screw nuts and screw heads.

FIGS. 2 a, 2 b, 3 a and 3 b show an airbag satellite on a mounting plate7 from the front and from the back respectively. The back here refers tothe side of the airbag satellite facing the mounting plate. Thearrangement of the satellite on the mounting plate 7 is explained withreference to these Figures:

After insertion of the satellite, the guiding lugs 5 engage in theguiding means 12 of the mounting plate 7 (FIG. 2 a). The satellite isthereafter brought into the mounting position. This can be done manuallyor mechanically. Displacement takes place in the direction of the arrow.In this mounting position, the fastening screws 4 are tightened with theaid of a mounting tool (FIG. 2 b).

FIGS. 3 a and 3 b show the same arrangements from the back.Counter-screws 6 in FIG. 3 b as a mounting counter device of fasteningscrews 4 from FIG. 2 a are arranged over a tapering of the two guidingmeans 12 such that, screwed down, they can provide the air bag satellitewith the necessary hold.

In the case of the acceleration sensor device (the airbag satellite)described thus far, the housing 1 can be fashioned such that access witha mounting tool to the fastening screws 4 and fastening of the airbagsatellite is possible in its mounting position. This is achieved bymeans of the elastic connecting bridge 10.

As shown in the embodiment according to FIG. 2 a, the connecting bridge10 is arranged between the deflectable ends of the two parallel springbars 11.

The connecting bridge 10 is deflected in an end position as shown inFIG. 2 a. Access to the fastening screw 4 which lies nearest to theconnecting bridge is thereby prevented.

In its rest position, shown in FIG. 2 b, the elastic connecting bridgeis deflected to the extent that access with a mounting tool to thefastening screw is possible.

The housing of a sensor device according to the present invention ismanufactured for the most part from plastic. Like any material, plasticcan be deformed without breaking up to a maximum mechanical loading. Inorder, in the embodiment according to FIGS. 1 a and 1 b, to protect theconnecting bridge 10 and the spring bars 11 against too high amechanical loading (and in particular against material failure) a springtension limiter 13 is provided. This is fashioned in the form ofmechanical lugs on both sides of the ends of the spring bars 11.

As shown in the embodiment, it is advantageous to fashion the springbars 11, the connecting bridge 10 and the spring tension limiter 13 asone piece with the housing 1. The sensor device then comprises fewercomponents, as a result of which the cost of manufacture and assembly isreduced.

The method for mounting an airbag satellite is described below withreference to FIGS. 2 a and 2 b:

The sensor device is first inserted with a guiding element, for examplewith the guiding lugs 5 on the spring element 9, into the guiding device12 of the mounting plate 7 (cf. FIG. 2 a).

The sensor device is then displaced over the mounting plate 7, wherebythe direction of displacement is predetermined by the guiding device 12(direction of arrow in FIG. 2 a). This can be effected manually orautomatically.

In the mounting position of the airbag satellite, the guiding element 5of the sensor device engages in the guiding device 12 of the mountingplate 7 (see FIG. 2 b).

The airbag satellite is then rigidly fastened on the mounting plate 7with a mounting device.

When the satellite is displaced, the spring element 9 and in particularits spring bars 11 are deformed. In the mounting position, the springbars 11 relax as the guiding lugs 5 engage in the guiding device 12 ofthe mounting plate 7 (see FIG. 2 b).

In an alternative method, a spring element is arranged on the mountingplate 7. The guiding element 5 of the airbag satellite can in this casebe fashioned rigidly:

FIG. 7 shows an airbag satellite on a mounting plate 7 on which a springelement 14 is arranged. If the satellite is displaced in the directionof the arrow, the spring element 14 is deformed until the guiding lugs 5have been guided past said spring element. The satellite is then engagedin its mounting position.

The airbag satellite is then rigidly fastened on the mounting plate 7with a mounting device.

In a further embodiment of the method, access of a mounting tool to themounting device 4 and fastening of the airbag satellite on the mountingplate 7 are enabled in the mounting position of the airbag satellite.The principle is explained using FIGS. 2 a and 2 b: the connectingbridge 10 of the spring element 9 of the sensor device is deflected toan end position (see FIG. 2 a), but rests in a rest position (see FIG. 2b).

A mounting tool can access the mounting device 4 of the sensor deviceeither in the end position or rest position of the spring element 9 andfasten the satellite rigidly on the mounting plate 7.

The spring element 9 does not have to be fully deflected, for exampleuntil a mechanical stopping point is reached, in the end position. Theend position and the rest position of the connecting bridge 10 arecharacterized rather by the fact that access to the mounting device 4and fastening of the airbag satellite on the mounting plate are eitherenabled or prevented.

The connecting bridge 10 preferably prevents access of a mounting toolto the mounting device 4 during displacement of the airbag satelliteover the mounting plate 7 to the mounting position. In the mountingposition, a mounting tool then access the mounting device 4 and fastenthe airbag satellite rigidly on the mounting plate 7.

In the method according to the invention the satellite has to beactively displaced, either mechanically or manually. Alternatively, theguiding device 12 can be formed such that the guided displacement of theairbag satellite is driven by the spring tension of the preloaded springelement 9. A possible arrangement is shown in FIG. 4.

In order to insert the airbag satellite into the guiding device 12, thespring element 9 has to be mechanically preloaded. The guiding device 12of the satellite are arranged obliquely relative to the direction of thearrow such that the spring tension of the spring element 9 and of theelastic connecting bridge 10 is released as a result of the springelement 9 moving to the mounting position. After insertion of the springelement 9 into the guiding device 12 the airbag satellite thereforemoves without any further external assistance to its mounting positionuntil the guiding element 5 engages with the mounting plate 7. Theairbag satellite is fastened in this position.

The sensor device according to the invention and the method according tothe invention for arranging a sensor device are described here only withreference to an airbag satellite. However, the invention covers allsensor devices which are arranged on a mounting plate and correspondingmethods for their arrangement.

1. A sensor device, comprising: a housing; a spring element including atleast two spring bars arranged substantially parallel having a guidingelement for displacing the sensor device over a mounting plate in aguided manner, wherein the guiding element is fashioned to cooperatewith a guiding device of a mounting plate; a mounting device on ahousing for arranging the sensor device on the mounting plate with theaid of a mounting tool; and an elastic connecting bridge arrangedbetween the at least two spring bars, wherein access to the mountingdevice with the mounting tool is prevented in a deflected position ofthe at least two spring bars by the connecting bridge, and access isenabled with the at least two spring bars in a released position, and inthe mounting position of the sensor device the at least two spring barsare in a released position.
 2. The sensor device according to claim 1,wherein the spring element, and the connecting bridge, are configured asone piece with the housing.
 3. The sensor device according to claim 2,wherein the elastic connecting bridge is arranged between deflectableends of the at least two spring bars.
 4. The sensor device according toclaim 1, wherein the spring element has a spring tension limiter.
 5. Thesensor device according to claim 4, wherein the spring tension limiteris configured as mechanical stops on both sides of ends of the springbars.
 6. A method for arranging a sensor device on a mounting plates,the sensor device having a spring element which comprises a guidingelement for displacing the sensor device over the mounting plate in aguided manner, and the guiding element is configured to cooperate with aguiding device of the mounting plate, comprising: inserting the sensordevice with a guiding element into the guiding device; displacing thesensor device along the guiding device over the mounting plate in aguided manner; engaging the sensor device in a mounting position withthe guiding element in the guiding device of the mounting plate; andfastening on the mounting plate in the mounting position with a mountingdevice, wherein the spring element in a deflected position preventsaccess with a mounting tool to the mounting device of the sensor device,such that access is enabled when the spring element is in a releasedposition.
 7. The method according to claim 6, wherein the spring elementis deflected during guided displacement of the sensor device along theguiding device such that access with the mounting tool to the mountingdevice of the sensor device is prevented, and in a mounting position ofthe sensor device such access is enabled.
 8. The method according toclaim 6, wherein access to the mounting device with aid of the mountingtool is prevented by an elastic connecting bridge which connects thespring element with two movable ends of the spring element of a two-partdesign in the form of two spring bars arranged parallel.
 9. The methodaccording to claim 6, wherein spring tension of the spring elementcauses the sensor device to be displaced over the mounting plate in aguided manner.